(a) Field of the Invention
The present invention relates to a telecommunication device including a housing having improved heat conductivity and, more particularly, to a heat radiation structure of the housing of a telecommunication device.
(b) Description of the Related Art
A gas-assist injection molding (GAIM) technique is widely used for molding a variety of plastic materials because the GAIM technique provides an improved appearance without an undesired projection or warp on the surface, and an improved strength and a light weight due to the structure of the hollow space.
For example, the interior accessories of a vehicle or television cabinets are manufactured by using the GAIM technique due to the improvement of the quality in the injection-molded parts, as well as the needs for smaller weight and dimensional accuracy in the interior accessories and the television cabinets.
Among other devices, a telecommunication device such as a base station of a personal handyphone system, which is generally attached onto a mast, is requested to radiate the internal heat generated by the integrated circuit therein, and have a housing with a smaller weight and smaller dimensions for achieving a lower cost.
The GAIM technique is not used heretofore in manufacture of the housing through which efficient heat radiation is requested, because the plastic material formed by the GAIM technique has lower heat conductivity compared to a metallic material.
Aluminum is generally used heretofore as the material for a housing of the base station of a personal handyphone system due to the excellent heat conductivity thereof. However, since the aluminum housing is generally formed as a solid body, the heat radiation capability of the aluminum housing is limited by and does not exceed the heat conductivity property of the aluminum metal.
Incorporation of metallic powder such as aluminum or copper into the plastic material may improve the heat conductivity of the plastic housing; however, the improved heat conductivity is yet far inferior to the heat conductivity of the solid metal itself.
Patent Publication JP-A-7-094881 describes a heat radiation structure of an electric equipment such as a computer. The heat radiation structure includes a cooling device for cooling therein refrigerant, a plurality of cooling modules through which the refrigerant passes, a tube system including supply paths and return paths between the cooling device and the cooling modules for circulating the refrigerant, and a plurality of pivot valves each disposed for a return path of a corresponding cooling module and having an extendable rod for controlling the flow rate of the refrigerant passing through the pivot valve based on the temperature of the refrigerant.
The heat radiation structure described in the above publication, however, has a complicated structure due to provision of the pivot valves for controlling the flow rate of the refrigerant through the cooling modules.
Patent Publication JP-A-2000-340978 describes a heat radiation structure of a telecommunication device, wherein a heat radiator having a plurality of heat radiation fins are attached onto the inner surface of the housing of the telecommunication device. Each of the heat radiation fins includes therein a heat pipe extending in the vertical direction for assisting the flow of the heat in the heat radiation fin, thereby improving the heat conductivity of the heat radiation structure without increasing the dimensions of the heat radiation fin.
Fabrication of the heat radiation structure of the telecommunication device described in the latter publication, however, is also complicated due to the provision of the heat pipes within the heat radiation fins.